| Abstract: | Three synthetic strategies were explored to lower the melting point of poly(4-hydroxybenzoate) below 400°C. Binary copolyesters of 4-hydroxybenzoic acid and 3-substituted 4-hydroxybenzoic acid were highly crystalline, regardless of composition, and did not melt below 400°C. In contrast ternary and quartenary copolyesters containing 3-bromo-4-hydroxybenzoic acid may possess melting points below 360°C. Binary copolyesters of 4-mercaptobenzoic acid and 3-substituted 4-hydroxybenzoic acids melt in the range of 360–400°C. Random copolyesters of 3-(4-hydrophenyl) propionic acid and 4-hydroxybenzoic acid are mainly amorphous with glass-transition temperatures between 50 and 15°C. They contain liquid-crystalline domains, which in the case of the 1:1 copolyester are stable over a range of ca. 400°C. The heat-distortion temperatures are low (60–80°C) due to the predominant influence of the amorphous matrix. |
